1. Field of the Invention
The subject invention is directed to a stamp formed connector for joining at least two conventional upstream exhaust pipes to at least one conventional downstream exhaust pipe.
2. Description of the Prior Art
The typical prior art exhaust system includes at least one manifold for collecting exhaust gas produced by the cylinders of an internal combustion engine. A pipe delivers the exhaust gas from the manifold to a catalytic converter where certain objectionable pollutants are converted into a less objectionable form. Another pipe extends from the catalytic converter to a muffler which attenuates noise associated with the flowing exhaust gas. At least one tail pipe then extends from the muffler to a location on the vehicle where the exhaust gases can be safely emitted.
The exhaust system becomes very hot, and must be routed to ensure sufficient clearance from parts of the vehicle that could be damaged by heat. This exhaust system routing also must pass through locations that are sufficiently large to accommodate the catalytic converter and the muffler. These controls on the location of exhaust system generally result in a very circuitous alignment.
Exhaust system routing is particularly complex for V-engines, such as V-8's or V-6's. The cylinders of a V-engine are disposed in two angularly aligned planes and emit exhaust gases from opposite respective sides of the engine. As a result, two separate exhaust pipes must extend from the spaced apart manifolds of the V-engine. Some vehicles with V-engines include entirely separate exhaust systems, with separate catalytic converters, separate mufflers and separate tail pipes. However, these systems are costly, and can further complicate the efforts to locate the respective catalytic converters and mufflers. As a result, most vehicles with V-engines have the respective exhaust pipes converge and join at a location upstream from the catalytic converter. Thus, the exhaust gas streams from each of the two manifolds on the V-engine typically communicate with a single catalytic converter and a single muffler.
Noise produced by an internal combustion engine is actually a series of repeating noises corresponding respectively to the sequential controlled explosions taking place in the cylinders of the engine. Engineers examine the loudness and frequency of noise resulting from these explosions, and design an appropriate array of tubes and chambers in a muffler for attenuating the observed noise. The task of designing a muffler is made more difficult if the noise from the respective explosions does not define a uniform and repetitive pattern approaching the muffler. A non-uniform pattern may cause sound waves from one explosion to partly overlap sound waves from a subsequent explosion. The additive effect of these overlapping noise patterns can complicate the acoustical tuning of the exhaust system.
Most properly timed engines will produce uniform firing of the cylinders, and hence have the potential to direct a uniform series of noise patterns to the muffler for attenuation. However, V-engines with a single muffler often have different exhaust gas travel lengths between the respective manifolds and the muffler. If possible, engineers will try to route the exhaust pipes for a V-engine to achieve substantially equal lengths between the respective manifolds and the point where the exhaust pipes converge. Although this objective is desirable, it is difficult to achieve. In particular, the typical engine compartment is extremely crowded, and engineers have few options for re-routing pipes to achieve the equal lengths. Additionally, the few options that may permit substantially equal lengths of pipes extending from the manifolds may bring the upstream and downstream exhaust pipes together at angles that are difficult or impossible to miter and weld properly. The complex mitering and welding to join the upstream and downstream exhaust pipes into a Y-shape is a time consuming procedure that is not well suited to a high degree of automation.
In the recent past, stamp formed connectors have been used to join two upstream exhaust pipes to a single downstream exhaust pipe. For example, U.S. Pat. No. 5,134,852 shows a pair of opposed stamped plates that are formed to define a first inlet, an outlet linearly aligned to the first inlet and a second inlet angularly aligned to both the first inlet and the outlet. The stamp formed connector shown in U.S. Pat. No. 5,134,852 avoids the need to miter and weld the pipes. However, the required linear alignment of the outlet pipe to one of the inlets would limit the options available for achieving equal lengths between the manifolds and the location at which the upstream exhaust pipes converge.
A very desirable stamp formed connector for achieving equal length exhaust pipes is shown in U.S. patent application Ser. No. 103,974 which is assigned to the assignee of the subject invention. The connector shown in U.S. patent application Ser. No. 103,974 consists of two plates that are stamp formed with channels disposed for defining exhaust passages between the plates. The passages include a pair of inlet passages and an outlet passage which converge at a selected location between the plates of the connector. The passages are curved to achieve a selected routing of the exhaust system components and to substantially equalize the travel length for exhaust gases traveling toward a muffler. By achieving these equal travel lengths, the noise pulses from the engine will arrive at the muffler uniformly and predictably. Thus, acoustical tuning of the muffler downstream from the connector is facilitated.
Although the connector shown in U.S. patent application Ser. No. 103,974 is extremely effective, there are still situations where it is difficult to compensate for differential pipe lengths between the manifolds and the point of convergence within the connector. In particular, the range of options for forming curved passages within the connector are limited by the space available for the connector and the amount of metal deformation that can take place within that space. These options may not be sufficient to offset the differences in exhaust gas travel lengths upstream of the connector.
Connectors also can complicate acoustical tuning and design. In particular it is difficult to predict the exact acoustical effect of the converging exhaust flows, or to determine the precise location for the convergence to take place. A significant amount of trial and error is required to achieve the best system design. However trial and error can be time consuming with both the prior art miter-and-weld connectors and the prior art two-piece stamp formed connector.
In view of the above, it is an object of the subject invention to provide a connector with an enhanced ability to achieve equal lengths for exhaust pipes.
Another object of the subject invention is to provide a stamp formed connector that avoids excessive deformation of the sheet material from which the connector is formed.
An additional object of the subject invention is to provide a stamp formed connector that enables inlet and outlet pipes to be placed in very close proximity to one another.
Still another object of the subject invention is to provide a stamp formed connector that enables optimum alignment of pipes leading to and from the connector.